Multi-scale simulation of freeze-thaw damage to RC column and its restoring force characteristics

The frost damage of reinforced concrete (RC) is of great complexity than plain one tested in laboratory, because of damage levels depending on various shapes and scales of structures, ambient conditions as well as detailed arrangement of reinforcing bars. In fact, damaged parts of locality in structural concrete may not contribute equally to overall mechanical performances. This paper presents an integrated life-time simulation which starts from the micro-pore formation and follows micro-scale frost action to the non-uniform frost damage considering temperature distributions, arrangement of reinforcing bars as well as the water uptake from the boundary, and finally to structural mechanical performances such as capacity and ductility. In this study, RC columns are simulated after different numbers of freeze-thaw cycles (FTC) and following repeated loads in order to investigate the seismic performances affected by frost damage. The numerical results clearly show the non-uniform damage of 3D extent at early FTC, which is closely related to the temperature field and reinforcement layout. The later stage of FTC shows localized frost damage, which mainly attributes to water filling in existing cracks. The seismic responses are also examined by comparing with previously reported experiments, and fair reproduction of restoring force characteristics is verified. Finally, the effect of lateral tie reinforcement is investigated numerically, and its effects on frost damage itself, as well as the residual seismic performances are discussed in detail.